1. Field of the Invention
The present invention relates to image data enhancement and compression methods and more particularly to methods of filtering data for enhancement and compression of graphic images and for efficient data storage and transmission.
2. Description of Prior Art
In the prior art there many image data compression methods. The following are systems representative of the prior art.
A paper by Spencer and Huang, presented at the Symposium on Computer Processing in Communications, Apr. 8-10, 1969, addresses the problem of transforming a gray scale image to an equivalent set of black/white images called bit planes. Although the paper discusses bit plane encoding and choice of code for efficient compression, the paper does not show a method for compressing edge pixel data in a second bit plane of a graphics image based on a determination of the first bit plane intensity value of each pixel.
Co-pending U.S. application Ser. No. 429,658, assigned to the same assignee as the present application describes a filter for gray scale image data which forces a least significant bit of a current pixel to be equal to a most significant bit of the current pixel in a two bit per pixel code when the most significant bit of the current pixel is equal to the most significant bit of a previous and a next pixel on the current scan line of an image. The method of this patent employs horizontal redundancy to filter abrupt changes in gray scale pixel values along a scan line. The patent does not show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
An article in the IBM Technical Disclosure Bulletin, Vol. 22, No. 7, December 1979, at page 2980 and following shows a method for coding gray scale image data employing a vertical redundancy scheme. The publication shows a method for coding pixel values for gray level runs of pixels along a line by comparing the value on the current line to the value on the line above in the image. The publication does not show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
U.S. Pat. No. 4,006,298 generally discloses a system having an image gray scale using 64 discrete levels of brightness. The patent does wnot show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
U.S. Pat. No. 4,177,470 shows a system wherein a binary data signal is operated on to reduce the number of bits in the signal without reducing information content of the signal. The patent shows basically a data compression system. The patent does not show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
U.S. Pat. No. 4,210,936 shows a method and apparatus which achieves compression of image data by a reduction matrix which utilizes less gray scale data than is generated from the original picture element matrix. For example, if a picture element gray level required four bits of data, then the reproduction of the gray scale requires only one bit of data. The patent does not show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
U.S. Pat. No. 4,229,768 teaches an apparatus which compresses binary image signals by a selective run length compression technique. The patent does not show a method for compressing edge pixel data in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
U.S. Pat. No. 4,280,144 discloses apparatus and method for improving quality of a coarse scan, line print image processing system. An encoder assigns a code to a coarsely scanned picture element representative of the reflectance characteristic thereof. For fine reproduction of coarsely scanned data, the coarsely scanned picture element is summed with at least four adjacent horizontal and vertical picture elements to reproduce a fine picture element comprising at least four sub-elements. Although the patent obtains information for determining a fine value of a particular picture element from adjacent picture elements, the patent in effect teaches a method for expanding data from a coarse scan to a fine representation and does not in fact filter image data. The patent does not show a method for compressing edge pixel in a second bit plane of a graphics image by determining whether the edge pixel under consideration has a maximum intensity value such as black or white or an intermediate intensity value.
The prior art discussed above does not teach nor suggest the present invention as disclosed and claimed herein.